Measures of temporal acuity have been shown to correlate strongly with speech perception tests, but rather weakly with the pure-tone audiogram. Temporal acuity measures are therefore a promising tool as a speech- performance-predicting index to supplement the audiogram. The purpose of this research is to evaluate two measures of temporal acuity, temporal gap detection and temporal onset simultaneity. These two measures fulfill many of the criteria that are desirable in achieving a clinical tool to supplement the audiogram. Gap detection and onset simultaneity thresholds will be measured to (1) resolve procedural issues that remain for simple stimuli, (2) evaluate a range of conditions of speech-like stimulus complexity and listener uncertainty, and (3) provide data for computer models of temporal acuity processes and deficits. The computer models will aid us in dissociating the confounding roles of audibility and frequency selectivity deficits from the temporal acuity deficits of hearing-impaired listeners. Normal-hearing listeners and groups of hearing-impaired listeners with similar audiograms, but dissimilar speech discrimination scores, will provide temporal acuity data. These psychoacoustic and modeling results will ultimately guide the development of an audiometric tool to aid the clinician in predicting and compensating for a wide range of speech perception deficits among patients who exhibit similar audiograms.